One-Step Anodic Synthesis of Gd-Doped TiO2 Nanotubes for Enhanced Photocatalysis

Traditional methods for preparing rare-earth-doped TiO2 nanotubes are multi-step and often result in uneven dopant distribution, while pure TiO2 is limited by its wide bandgap and rapid charge recombination. In this study, a one-step in situ synchronous anodization strategy is developed to fabricate gadolinium (Gd)-doped TiO2 nanotube arrays directly on a titanium substrate. By adding gadolinium nitrate to an ethylene glycol–NH4F electrolyte, Gd incorporation and nanotube growth are achieved simultaneously, reducing the processing steps by over 60%. The obtained Gd–TiO2 nanotubes exhibit extended visible-light absorption with an edge beyond 500 nm and show a methylene blue degradation efficiency of 90% within 60 min, which is 50% higher than that of undoped TiO2. Scavenger experiments reveal that ·OH radicals play the predominant role in the photocatalytic process. First-principles calculations further confirm significant bandgap narrowing from 2.89 eV to 2.46 eV after Gd doping. This work provides a simple, efficient, and scalable synthesis route for high-performance TiO2-based photocatalysts with enhanced solar-driven activity.